The term “decoder,” which will be used as an exemplary implementation of a terminal, as used herein may refer to a decoder physically separate from a receiver, a combined receiver and decoder, such as in a set-top box (decoder), or a decoder having additional functions, for example recording devices, displays or web browsers. It will also be assumed that the general concepts of conditional access systems are well known and that they, as such, will not need to be described further hereinafter where this is not needed for the comprehension of the invention.
Conditional access systems, such as Pay TV that will be used throughout the description, has gained wide acceptance in many countries. Many households have a decoder, and a majority of households have more than one TV set. Currently, with one decoder, a subscriber can often access Pay TV programmes on only one TV set. Two main solutions have been proposed to solve this problem.
A first solution is to distribute the received content within the household. The current state of the art is to use wireless analogue retransmission. Unfortunately, the video quality is bad and it is only possible to watch one and the same program on all the connected TV sets.
A second solution is to simply provide more decoders in the household. Many broadcasters offer a second, cheaper subscription to households that already have a subscription. However, as broadcasters fear that neighbours or relatives will “share” the two subscriptions to get an average lower price for their subscriptions, they request that the two decoders should be paired. FIG. 1 illustrates the basic, prior art concept. Two decoders 11, 12 are linked through a bi-directional digital connection 13. One decoder 11 acts as the master and the other decoder 12 acts as the slave. The master 11 is always able to access programs authorized by the subscription, while the slave 12 is able to access programs authorized by the subscription only if it is connected to the master 11.
Several methods exist to verify that the two decoders are used together.
One solution, proposed by some conditional access (CA) providers is to use dedicated Entitlement Management Messages (EMMs). The master decoder 11 receives, apart from the EMMs directed to it, also the EMMs intended for the slave decoder 12, and sends the latter EMMs to the slave 12 over the digital connection 13. While other, more complex solutions exist, it will be appreciated that even this relatively simple solution implicates big modifications of the CA system and a strong linking with the broadcaster's back office, and that it is, for these reasons, impractical, if not unusable, in a horizontal market.
WO 2004/019296, “Secure Electric Anti-Theft Device, Anti-Theft System Comprising One Such Device and Method of Matching Electric Devices”, describes a method that ensures pairing between several networked devices. To fully operate, a device requires the presence of the security device it was imprinted to during an initialisation phase. Although this method could be used to pair decoders, it would mean that a master decoder and a slave decoder are differentiated, which is a problem for the manufacturer, the retailer, and the after-sales staff.
WO 03/105437, “Method, System and Terminal for Receiving Content with Authorized Access”, describes another method that ensures pairing between several networked devices. A secondary device (i.e. a slave device) is able to access content only if it is paired with, and can communicate with, a predetermined principal terminal (i.e. a master) with which it has been paired initially. This method as well is limited in some situations in that there is a certain lack of flexibility, since for example a slave decoder must be paired with a particular master for it to work. As before, this is a problem for the manufacturer, the retailer, and the after-sales staff.
It can therefore be appreciated that there is a need for a flexible solution that makes it possible to turn, in a controlled and reliable fashion, a decoder into a master decoder or a slave decoder. The transformation should preferably occur in the subscriber's home (or equivalent location). Furthermore, the solution should also ensure the pairing between a master decoder and a slave decoder. This invention provides such a solution.